It is well known that prebiotics comprise carbohydrates and more specifically, oligosaccharides. Furthermore it is known that they have widely been used as functional food ingredients. They resist hydrolysis by enzymes of the human digestive tract, can reach the colon undegraded and provide a carbohydrate substance particulary suited to the growth of bifidobacteria Oligosaccharides may be produced from glucose, galactose, xylose, maltose, sucrose, lactose, starch, xylan, hemicellulose, inulin, gum or a mixture thereof. Purified commercially available products such as fructooligosaccharides contain greater than about 95% solids in the form of oligosaccharides.
Fructooligosaccharides have been studied in humans mainly for functional claims related to the bioavailability of minerals, lipid metabolism and and regulation of bowel habits (Roberfroid, M. B. Delzenne, N. M. Annu Rev Nutr 1998;18:117-143). Little attention has been given to their effect on immunological functions, while indications for modifications of carcinogenesis and stimulation of gut-associated lymphoid tissue comes from animal studies (Pierre, F., et al. Cancer Res 1997;57:225-228) .
Indeed, fructooligosaccharides, long (inulin) and short chain (oligofructose) are among the carbohydrates, which escape digestion in the upper gastro-intestinal tract. They are then fermented in the colon and selectively stimulate the growth of bifidobacteria.
Human intestinal flora with its important metabolic activity is possibly associated with many health related functions such as maintenance of gut homeostasis, metabolism of xenobiotics and stimulation of gut immunity. It is influenced by disease, diet, stress and possibly ageing. The large intestine contains up to 1012 bacteria/g faeces with about 103 different species from approximately 40-50 genera of bacteria. Most of them are obligate anaerobes with a large population, however, of facultative anaerobes. The main anaerobe species are Bacteroïdes, bifidobacteria, eubacteria, which make up to 99% of the total faecal flora, followed by clostridia, lactobacilli and gram positive cocci, enterococci, coliforms, methanogens and at much lower levels sulfate-reducing bacteria (Hill, M. J. Normal gut bacterial flora. 1995;3-17).
Adult microflora characteristics are present from about 2 years of age. Adult gut microflora seems to be rather stable; although some changes have been reported with ageing, mainly low levels of bifidobacteria and Bacteroïdes (Hopkins, M. J., et al. Gut 2001;48:198-205). Gut flora can be divided into species that have beneficial effects, such as bifidobacteria, or harmful effects, such as Pseudonioinas aeruginosa, Protezus species, staphylococci, some clostridia and Veilonellae, and species that are intermediate in effect such as enterococci, Escherichia coli, Enterococci and Bacteroïdes. Bifidobacteria and lactobacilli have been reported to have beneficial effects on specific immune functions (Schiffrin, E. J., et al. J Dairy Sci 1995;78:491-497).
With age it is generally reported that bifidobacteria are diminished, while Clostridim perfringens, Entercocci and Enterobacteriaceae are increased (Mitsuoka, T. Hayakawa, K. Zentralbl Bakteriol [Orig A] 1973;223:333-342). Bacterial overgrowth occurs more frequently in the elderly due to the high prevalence of atrophic gastritis and hypochlorhydria. Bacterial overgrowth seems to be free of clinical symptoms in healthy elderly, it may have some importance in frail elderly ≧75 year of age, and Clostridium difficile associated diarrhea is more frequent in the elderly in acute care or long-term care, in association with antibiotic treatment and possibly decreased immune response. Ageing is related with a loss in immune function and the existence of an interrelationship between nutrition and immune function has been recognized (Meydani, S. N. Status of Nutritional Immunology Studies: J Nutr Immunol 1994;2:93-97).
Changes in immune response (remodeling of cytokine production and dysregulation of the immune functions) is associated with increased incidence of infections and mortality linked to infection. Nutritional interventions, mainly vitamin and mineral supplementation, can improve the immune response in frail elderly [Lesourd, B. M. Am J Clin Nutr 1997;66:478S-484S41].
The present invention aims to provide another composition able to limit the dysregulation of the immune function, and more particularly the abnormal activation of non-specific immune response such as the phagocytes and the monocyte macrophage cell system as well as preserve lymphocyte subpopulations in normal level of activation.